Fix for issue 27199

tests/compiler/dart2js_extra/27199_test.dart

+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Regression test for http://dartbug.com/27199 in --checked mode.
+
+// Typedefs must be unaliased at some point before codegen to have the correct
+// number of references.  The unaliased type of ItemListFilter<T> has two
+// references to T: (Iterable<T>) -> Iterable<T>.
+typedef Iterable<T> ItemListFilter<T>(Iterable<T> items);
+
+class C<T> {
+  Map<String, ItemListFilter<T>> f = {};
+}
+
+main() {
+  var c = new C();
+  var a = 12;
+  if (new DateTime.now().millisecondsSinceEpoch < 42) a = {};
+  c.f = a;
+}